The present invention relates to an optical recording disk and a manufacturing method thereof, and more particularly, it relates to an optical recording disk which is superior in quality, which is good in yield, and which can be easily manufactured, as well as a manufacturing method thereof.
Conventional methods in which concentric or spiral grooves for tracking are formed in the surface of a substrate, include a method in which a substrate and grooves are integrally formed through plastic injection molding, and a so-called 2P (Photo-Polymerization) method in which a transfer layer having grooves therein is provided on a substrate.
Of those two methods, in the latter 2P method, manufacturing is made through the steps as shown in FIGS. 5 through 9. In FIG. 5, after ultraviolet setting resin 2 is applied onto a groove forming original disk A (hereinafter referred to "a stamper") or a substrate which is made of optical glass or acrylic resin, then, the stamper A and the substrate 1 are pressed together. Thereafter, as shown in FIG. 6, ultraviolet rays 3 are radiated through the substrate 1 to thereby harden the ultraviolet setting resin 2. After completion of the hardening reaction, the ultraviolet setting resin integrated with the substrate 1, that is, a transfer layer 4, is peeled from the stamper A, so that the groove pattern of the stamper A is transfer-duplicated on the surface of the hardened transfer layer 4, as shown in FIG. 7. A recording layer 5 is laminated on the surface of the transfer layer 4, as shown in FIG. 8, and another substrate 8 is bonded onto the recording layer 5 through an adhesive-agent layer 7, thereby manufacturing an optical recording disk, as shown in FIG. 9.
In the transfer duplicating step for forming grooves in manufacturing an optical recording disk as described above, first, the ultraviolet setting resin 2 which is a material of the transfer layer is dropped onto the stamper A or the substrate 1 as shown in FIG. 10, and the stamper A or the substrate 1 is rotated so that the ultraviolet setting resin 2 is annularly applied to thereby form a ring portion 10.
Next, as shown in FIG. 6, the stamper A and the substrate 1 are pressed on each other so that the ultraviolet setting resin 2 is extended between the stamper A and the substrate 1, as shown in FIG. 11, and then the ultraviolet setting resin is hardened through radiation of ultraviolet rays to thereby form the transfer layer 4. In order to peel the transfer layer 4 from the stamper A, for example, a pair of grasping pads grasp an inner hole 70 of the substrate 10 from their opposite outer sides. After that, a peeling gas such as a nitrogen gas or the like is supplied to the inner circumferential side of the disk, so that the transfer layer 4 integrated with the substrate 1 is peeled from the stamper A.
However, this conventional transfer duplicating step has a problem that, in order to supply a peeling gas such as nitrogen gas or the like into the inner circumferential side of the transfer layer 4, it is necessary to lift up the inner circumferential side of the transfer layer 4 so as to peel the small portion of the transfer layer 4 from the stamper A. For the purpose of peeling, a large pressure is required, and if the pressure is not correctly applied, breakage and damage of the substrate can result.